This invention relates to an adjustment screw and more particularly to an adjustment screw assembly having rocker arms for a combustion engine.
Adjustment screws are commonly utilized in combustion engine applications to provide a pivotal linkage and fine tune the interconnection between rocker arms, valves and fuel injector followers. For diesel engine applications, the adjustment screw is also utilized as the pivotal linkage between the rocker arm and a fuel injector follower. The adjustment screw must be adjustable to manage clearance, and therefore clatter, between the adjustment screw and valves or fuel injector follower. Furthermore, when the adjustment screw is used for fuel injector follower applications oil lubrication is required between the follower and the adjustment screw. This oil is supplied internally through the rocker arm.
The adjustment screw has a lower button and a vertical member. The vertical member engages adjustably to the rocker arm and the lower button engages pivotally to the vertical member. A resilient clip device is typically used to connect the lower button to the vertical member. The clip assures that the lower button does not fall away from the vertical member during assembly of the combustion engine. After assembly, the clip serves no further function because a spring of the combustion engine provides an upward force which holds the lower button against the end of the vertical member. In addition, clearances are such that it does not allow the button to come out. Although the clip is required only during assembly, the clip is not readily removable from the adjustment screw and therefore remains installed throughout the useful life of the combustion engine. Unfortunately, the clip is a latent concern, with a possibility to fragment during prolonged operation of the combustion engine. Any fragments have a possibility to become lodged within the engine block or entrained within the lubricating oil, thereby creating an engine operation and warranty concern.
The invention provides an adjustment screw assembly having a pivoting rocker arm for a combustion engine. The adjustment screw has a vertical member having an upper end threaded adjustably to the rocker arm and a lower end. An upper end of a lower member is pivotally connected to the lower end of the vertical member forming a pivotal connection. The pivoting action of the rocker arm causes the adjustment screw to oscillate which in turn causes a linear up and down movement of an actuator through contact of a bottom surface of the lower member to a top surface of the actuator. Because the contact is continuous and the bottom surface remains parallel to the top surface, the bottom surface slides back and forth transversely across the actuator""s top surface as the actuator moves up and down. Preferably, the actuator is either valves or a fuel injector follower for a diesel engine.
The pivotal connection comprises a male connector snap fitted inside a female socket. The female socket has an engagement lip portion having an inner edge centering about a female socket centerline. The male connector has an outer perimeter centering about a male connector centerline. A male connector diameter of the outer perimeter is slightly larger than an inner edge diameter, thereby forming the snap fit as the outer perimeter of the male connector is forced past the inner edge of the female socket. Preferably, to accomplish the snap fit, the female socket centerline is offset to the male connector centerline at a prescribed angle during the snapping action. The female socket may either be the upper end of the lower member or the lower end of the vertical member, and vice-versa for the male connector.
By use of this snap fit lower member, it is possible to eliminate the clip once used to secure the lower member to the vertical member thereby rendering a reduction of parts used to construct the adjustment screw.